The Sangheili Effect
by Allard-Liao
Summary: Years after the Covenant Remnant founded by Jul M'dama had been destroyed, a new Covenant of Prophet-led Brutes attempt to attack humanity and its allies. One of the task forces sent to squash the upstarts triggers an unprecedented Slip-Space event. This is my very, VERY long-overdue answer to the Crossover Challenge by B1ue Ange1s. Rated T for now.
Uncolonized System, 2569

Sangheili Separatist Battlecruiser _Cleansing Blade_

Shipmaster Lor'an Taham watched from his chair as the ships under his command came out of Slipspace exactly where he had planned, practically on top of the Jiralhanae fleet. He smiled. The ruthless zealots had made their final mistake and tried to attack the Unified Species, the recent alliance between humanity and the former member-species of the Covenant. Lor'an's battlegroup, which also included seven destroyers and over a dozen corvettes, was the vanguard for the US's counter-assault. The apes and their san'shyuum masters would burn.

"All ships, open fire. Let none of them escape." Pulse lasers, plasma torpedoes, and energy projectors streaked through the space between the two fleets. The brute ships, caught unawares, had their numbers reduced by half in the first volley, alone. Due to their orientation, most of their weapons could not fire back. "Keep out of their arcs of fire; all destroyer crews, try to circle around. Crush them in a pincer."

That was when the battle became a dirty brawl. One of the destroyers broke apart as three enemy frigates concentrated their full firepower on it. In return, the _Blade_ 's energy projector sliced all three frigates apart in one sweep. The brutes held the advantage in numbers, but the _Cleansing Blade_ and the quality of the Sangheili crews more than made up for it. The heaviest ship on the enemy side was a light cruiser, which was quickly dispatched by a volley of torpedoes from the _Blade_.

The skirmish did not last much longer after that. In desperation, the last enemy ship began to make a run for Slipspace. "Burn that ship. Now." As the energy projector reached out and impaled the destroyer, Lor'an's grin of triumph turned into a mandible-drop of horror as he realized that the ship's Slipspace drive was destroyed at the exact moment it released the energy intended to create the Slipspace rupture. As the sphere of energy radiated outward, he only had time to shout one word. "Brace!"

* * *

System Phi Clio, Rosetta Nebula, 2178

Quarian Ship _Idenna_

"Captain."

Ysin'Mal, captain of the _Idenna_ , walked over to the sensor station. "What is it?"

"Some kind of energy anomaly, the likes of which I've never seen or even heard of before. Take a look."

He brought up the feed from the visual sensors. There appeared to be a field of energy with a violet lining that shifted continuously. "Overlay an energy reading." There was no energy at all inside the anomaly, but the rim was emitting readings greater than some stars. "What is this thing?"

That was when well over a dozen ships spewed out of the anomaly. "Keelah!"

"Get a message to the admiralty board. We have, possibly, encountered either a new variety of geth ship or a new species entirely with a new method of FTL. Someone get me a read on those ships. I want to know who they are. Gunnery Chief, warm up weapons, but do not engage, yet; let me know if they power up their own weapons. Navigation, be ready to jump us to FTL if that happens."

The communications officer turned toward Ysin. "Captain, we're being hailed."

"Put them through with every translation VI we have."

Surprisingly, the deep voice on the other end seemed to be speaking the human tongue, English, if the translators reporting the source language were right. "Power down your weapons or we will burn you to vapor."

Ysin looked to the gunnery officer. "Do as he says." To the communications officer, he added, "Ask Admiral Gerrel to bring the Heavy Fleet here. Patch me in to the aliens' comm."

"Very good. Now, we will speak."

"Who are you?" The deep voice reminded the quarian Captain of a polite krogan, if such a thing was possible.

"Shipmaster Lor'an Taham of the sangheili. You?"

"Captain Ysin'Mal vas Idenna of the quarians. Where did you come from?"

"An uninhabited system a few hours journey from Doisac."

"Where?"

"Doisac. Home-world of the Jiralhanae."

"I've never heard of that species."

"Where are we now?"

"The Phi Clio system of the Rosetta Nebula."

A few seconds of dead air followed. "We have neither of those in our database. Do you know of Halo?"

"Just what I know from human myth…"

Ysin could swear she heard a relieved sigh. "Good. I will hope that they can help us return home to Sanghelios."

"…except there are no records of your species or home-world, even among those of the humans."

Silence. "This will sound insane. What year is it?"

"2178. Why?"

"We traveled here through a…unstable event from the year 2569. I need to speak with your leaders to help find a way home."

* * *

Citadel, Serpent Nebula, 2183

 _Where is he?_ Tali'Zorah nar Rayya paced. She needed to get the information stored in her omni-tool to the Shadow Broker. If anyone would accept her intel, it would be him. The door at the end of the alley opened and a turian flanked by two salarians in full armor walked toward her.

The salarians stopped at the foot of the stairs, while the turian kept coming. "Do you have it?"

"Where's the Shadow Broker? Where's Fist?"

He put his hand on her shoulder. "They'll be here." He stroked her arm. "Where's the evidence?"

She swatted his hand away. "No. The deal's off." The salarians leveled assault rifles at her. Before they could fire, she reached into one of her pockets, pulled out a plasma grenade, primed it and flicked it at one of the mercs. As he tried in vain to scrape it off his chest, she dove for cover and drew a plasma pistol in one hand and her shotgun in the other. An explosion signaled the demise of the salarian she stuck.

"Kill her!" The turian opened fire with a shotgun, combining suppressive fire with the remaining salarian.

Tali popped out of cover just long enough to unleash an overcharged shot on the turian, completely stripping his shields. A follow-up blast from her shotgun finished him off. She turned to shoot the other salarian when his head exploded from twin sniper shots. _Oh no._ Standing at the opposite end of the alley were a human, a turian, and a krogan, the former two stowing sniper rifles.

Hoping to deflect their attention, she shouted, "That bastard! Fist set me up."

The human offered his hand, palm up. "It's alright. You're safe now."

"Thanks for saving me. But who are you?"

"I'm Commander Shepard of the Alliance."

"Again, thank you, Commander. I wish I had a way to repay you for my life."

The turian, who she now noticed had the blue facial markings of a Palaven native, spoke up. "We were told you might have information about a traitor named Saren."

"Then I can begin repaying you right away. But I can't speak here."

The turian turned to the Commander. "We should go to your embassy. Your ambassador would want to see this evidence, anyway."

Shepard nodded and led the way to the human embassy.

* * *

SSV _Normandy_ , en route to Therum, 2183

It had been surprising, but Shepard had offered Tali the opportunity to join him on his quest to bring down now-disgraced Spectre, Saren Arterius, the same man who had ordered her assassination. She had accepted, but for a different reason. Saren was helping the geth who were trying to bring back an ancient super-machine race called the Reapers. The Reapers, viewed by the geth as synthetic gods, had driven the prothean race to extinction. The true goal of this mission, as Shepard had told the crew, was to stop Saren from succeeding in that objective.

Speaking of the Commander, Tali could hear him talking with Engineer Adams about the _Normandy_ 's drive core. She couldn't help but smile as she thought about it. The Tantalus was the most advanced drive core design in known Citadel space. Not as advanced as the sangheili Slipspace and hydrogen fusion drives, but it was still quite advanced.

The sound of someone clearing his throat brought back the quarian's attention. She turned around and saw Shepard was the one behind her. "Shepard, your ship is amazing! I never knew the Alliance had ships this advanced."

" _Normandy_ 's one of a kind. An advanced prototype."

"Heh. Back on the flotilla, we've had to make use of whatever ships we can get our hands on. Most of them are cast-offs and second-hand ships we've managed to purchase or salvage. Some even date back to the geth rebellion."

"That would make those ships hundreds of years old."

Tali crossed her arms and stood a little straighter. "We're very good at keeping things in working order."

"I'll bet. I do have a question, however."

 _Uh-oh._

"Where did you get that plasma gun?"

"It actually fires a phasic envelope wrapped around a standard mass accelerator round. Works wonders against synthetics and kinetic barriers."

"And you got your hands on it by-?"

"My father led the team that designed it. He's on the Admiralty Board, so he was able to bend the rules and give me one of the prototypes. It was a risk, but that pistol has saved my life a couple of times, now."

"Your father must really love you."

"Yeah. Although he doesn't always show it, he does."

At that moment, their conversation was interrupted as the pilot's voice came over the intercom. "We're ten minutes out from Therum, Commander. Might want to get your team ready."

"Thank you, Joker." He turned back to Tali. "I guess we'll finish this conversation another day."

"See you later." As he walked away, the young quarian slumped back against her console, grateful for the opaque visor covering her face. She hated having to lie to her captain, but the sangheili leader, Lor'an, had demanded that their existence be kept a secret until they were ready to reveal themselves to the galaxy.

She slowly became aware that Shepard had returned, this time wearing his armor and with his weapons on his back. "Tali, gear up."

Try as she might, she couldn't disguise her anxiety. Here she was, a little girl just going into adulthood, and she was being ordered to join the _first human SPECTRE_ in combat. Yes, she had received a few years of training from some of the sangheili's best warriors, but she was still a kid. "Yes, sir."

She walked over to the locker she had been assigned and pulled out her plasma pistol, which was attached to her hip, and her shotgun, which she slid into its slot along the small of her back. A chuckle drew her attention to her left, where the krogan mercenary, Wrex, leaned against the bulkhead, having already armed himself. "Nice gun."

The shotgun had started life as a krogan Claymore, but it had been so heavily modified that it didn't really qualify as one anymore. For one thing, it had been cut down to about three quarters of its original size, and its launching rails had been replaced by those of a portable anti-armor railgun supposedly created by the humans of the sangheilis' universe, which resulted in a much-lowered recoil while still maintaining much of its punch. The final result was a shotgun that packed a lot of power, had manageable recoil, and could, in a pinch, be fired one-handed. "Thanks. I pieced it together, myself."

"Then you're a damn good mechanic. I think I might ask you to look at my gun after this."

She gulped; she wasn't sure if she could improve his weapon without revealing a few classified technologies. "Maybe. No promises, though."

Shepard walked in front of them. "Atten-tion."

Tali snapped to attention, as did the turian, Garrus, while Wrex simply walked away from the wall and stood next to the other two non-humans. Garrus, being a member of a militaristic race as he was, spoke first. "What's the mission, sir?"

The human chuckled and began to pace in front of them. "At ease. Our most concrete link to Saren is Liara T'soni, the daughter of his asari advisor, Matriarch Benezia. Liara was last seen at an archaeological dig site on the planet Therum. Our mission is to go down to the site and extract her. We have no idea whether Liara is allied with her mother, but she is an expert on the protheans, so we need her either way. Nor do we know how much resistance, if any, we will face." He pointed to the Mako. "Mount up."

* * *

When they entered through the rear hatch, Shepard continued forward to the driver's seat. "Garrus, you've got gunner duty."

"Roger that." The turian clambered into the gunner's seat and activated the main cannon's control console.

A synthetic voice announced, "Main cannon, online. Co-axial machine gun, online. Turret control mechanisms, online. All systems nominal. Safety systems armed; this vehicle's weapons will not fire until the safeties are turned off."

"We're good to go on the guns. Just don't bump me around too much."

The internal radio of the IFV crackled to life. "Commander, we're entering Therum's atmosphere. Get ready to drop."

"Roger that, Joker. Everyone, brace yourselves."

As _Normandy_ swooped low, Shepard gunned the Mako's engine, accelerating out of the hangar and aiming for the smoothest patch of volcanic ground he could find.


End file.
